vue服務(wù)端渲染

一、什么是服務(wù)端渲染

客戶端請求服務(wù)器，服務(wù)器根據(jù)請求地址獲得匹配的組件，在調(diào)用匹配到的組件返回Promise (官方是asyncData方法)來將需要的數(shù)據(jù)拿到。最后再通過window.__initial_state=data將其寫入網(wǎng)頁，最后將服務(wù)端渲染好的網(wǎng)頁返回回去。接下來客戶端將用新的store狀態(tài)把原來的store狀態(tài)替換掉，保證客戶端和服務(wù)端的數(shù)據(jù)同步。遇到?jīng)]被服務(wù)端渲染的組件，再去發(fā)異步請求拿數(shù)據(jù)。

二、服務(wù)端渲染的環(huán)境搭建

這是vue官網(wǎng)的服務(wù)端渲染的示意圖，ssr有兩個入口文件，分別是客戶端的入后文件和服務(wù)端的入口文件，webpack通過兩個入口文件分別打包成給服務(wù)端用的server bundle和給客戶端用的client bundle.當(dāng)服務(wù)器接收到了來自客戶端的請求之后，會創(chuàng)建一個渲染器bundleRenderer，這個bundleRenderer會讀取上面生成的server bundle文件，并且執(zhí)行它的代碼， 然后發(fā)送一個生成好的html到瀏覽器，等到客戶端加載了client bundle之后，會和服務(wù)端生成的DOM進(jìn)行Hydration(判斷這個DOM和自己即將生成的DOM是否相同，如果相同就將客戶端的vue實例掛載到這個DOM上)
實現(xiàn)步驟：

1、創(chuàng)建vue實例（main.js）
importVuefrom'vue'
importAppfrom'./App.vue'
importiViewfrom'iview';
import{createStore}from'./store'
import{createRouter}from'./router'
import{sync}from'vuex-router-sync'
Vue.use(iView);
export functioncreateApp() {
conststore = createStore()
constrouter = createRouter()
sync(store,router)
constapp =newVue({
router,
store,
render: h => h(App)
})
return{app,router,store}
}

因為要做服務(wù)端渲染，所以這里不需要再用el去掛載，現(xiàn)將app、router、store導(dǎo)出

2、服務(wù)端入口文件（entry-server.js）
import{ createApp }from'./main'
constisDev = process.env.NODE_ENV !=='production'
const{ app,router,store } = createApp()
constgetAllAsyncData=function(component){
letstores = []
functionloopComponent(component) {
if(typeofcomponent.asyncData !=='undefined') {
for(letaofcomponent.asyncData({store,route: router.currentRoute})) {
stores.push(a)
}
}
if(typeofcomponent.components !=='undefined') {
for(letcincomponent.components){
loopComponent(component.components[c])
}
}
}
loopComponent(component)
returnstores
}
export defaultcontext => {
return newPromise((resolve,reject) => {
consts = isDev && Date.now()
const{url} = context
constfullPath = router.resolve(url).route.fullPath
if(fullPath !== url) {
reject({url: fullPath })
}
router.push(url)
router.onReady(() => {
constmatchedComponents = router.getMatchedComponents()
if(!matchedComponents.length) {
reject({code:404})
}
letallAsyncData = getAllAsyncData(matchedComponents[0])
Promise.all(allAsyncData).then(() => {
isDev && console.log(`data pre-fetch:${Date.now() - s}ms`)
context.state = store.state
resolve(app)
}).catch(reject)
},reject)
})
}

這個文件的主要工作是接受從服務(wù)端傳遞過來的context參數(shù)，context包含當(dāng)前頁面的url，用getMatchedComponents方法獲取當(dāng)前url下的組件，返回一個數(shù)組，遍歷這個數(shù)組中的組件，如果組件有asyncData鉤子函數(shù)，則傳遞store獲取數(shù)據(jù)，最后返回一個promise對象。
context.state =
store.state的作用是將服務(wù)端獲取到的數(shù)據(jù)掛載到context對象上，后面在server.js文件里會把這些數(shù)據(jù)直接發(fā)送到瀏覽器端與客戶端的vue實例進(jìn)行數(shù)據(jù)(狀態(tài))同步。

3、客戶端入口文件（entry-client.js）
importVuefrom'vue'
import'es6-promise/auto'
import{ createApp }from'./main'
importProgressBarfrom'./components/ProgressBar.vue'
// global progress bar
constbar = Vue.prototype.$bar =newVue(ProgressBar).$mount()
document.body.appendChild(bar.$el)
Vue.mixin({
beforeRouteUpdate(to,from,next) {
const{ asyncData } =this.$options
if(asyncData) {
Promise.all(asyncData({
store:this.$store,
route: to
})).then(next).catch(next)
}else{
next()
}
}
})
const{ app,router,store } = createApp()
if(window.__INITIAL_STATE__) {
store.replaceState(window.__INITIAL_STATE__)
}
router.onReady(() => {
router.beforeResolve((to,from,next) => {
constmatched = router.getMatchedComponents(to)
constprevMatched = router.getMatchedComponents(from)
letdiffed =false
constactivated = matched.filter((c,i) => {
returndiffed || (diffed = (prevMatched[i] !== c))
})
constasyncDataHooks = activated.map(c => c.asyncData).filter(_ => _)
if(!asyncDataHooks.length) {
returnnext()
}
bar.start()
Promise.all(asyncDataHooks.map(hook => hook({ store,route: to })))
.then(() => {
bar.finish()
next()
})
.catch(next)
})
app.$mount('#app')
})
if('https:'=== location.protocol && navigator.serviceWorker) {
navigator.serviceWorker.register('/service-worker.js')
}

if(window.INITIAL_STATE) {
store.replaceState(window.INITIAL_STATE)
}
這句的作用是如果服務(wù)端的vuex數(shù)據(jù)發(fā)生改變，就將客戶端的數(shù)據(jù)替換掉，保證客戶端和服務(wù)端的數(shù)據(jù)同步
Service Worker主要用于攔截并修改訪問和資源請求，細(xì)粒度地緩存資源。它運行瀏覽器在后臺，運行環(huán)境與普通頁面腳本不同，所以不能直接參與頁面交互。出于安全考慮，service worker只能運行在HTTPS上，防止被人從中攻擊。

4、創(chuàng)建服務(wù)端渲染器（server.js）
constfs = require('fs')
constpath = require('path')
constLRU = require('lru-cache')
constexpress = require('express')
constcompression = require('compression')
constresolve= file => path.resolve(__dirname,file)
const{ createBundleRenderer } = require('vue-server-renderer')
constisProd = process.env.NODE_ENV ==='production'|| process.env.NODE_ENV ==='beta'
constuseMicroCache = process.env.MICRO_CACHE !=='false'
constserverInfo =
`express/${require('express/package.json').version}`+
`vue-server-renderer/${require('vue-server-renderer/package.json').version}`
constapp = express()
consttemplate = fs.readFileSync(resolve('./src/index.template.html'),'utf-8')
functioncreateRenderer(bundle,options) {
returncreateBundleRenderer(bundle,Object.assign(options,{
template,
cache: LRU({
max:1000,
maxAge:1000*60*15
}),
basedir: resolve('./dist'),
runInNewContext:false
}))
}
letrenderer
letreadyPromise
if(isProd) {
constbundle = require('./dist/vue-ssr-server-bundle.json')
constclientManifest = require('./dist/vue-ssr-client-manifest.json')
renderer = createRenderer(bundle,{
clientManifest
})
}else{
readyPromise = require('./build/setup-dev-server')(app,(bundle,options) => {
renderer = createRenderer(bundle,options)
})
}
constserve= (path,cache) => express.static(resolve(path),{
maxAge: cache && isProd ?1000*60*60*24*30:0
})
app.use(compression({threshold:0}))
app.use('/dist',serve('./dist',true))
app.use('/static',serve('./static',true))
app.use('/service-worker.js',serve('./dist/service-worker.js'))
constmicroCache = LRU({
max:100,
maxAge:1000
})
constisCacheable= req => useMicroCache
functionrender(req,res) {
consts = Date.now()
res.setHeader("Content-Type","text/html")
res.setHeader("Server",serverInfo)
consthandleError= err => {
if(err.url) {
res.redirect(err.url)
}else if(err.code ===404) {
res.status(404).end('404 | Page Not Found')
}else{
// Render Error Page or Redirect
res.status(500).end('500 | Internal Server Error')
console.error(`error during render :${req.url}`)
console.error(err.stack)
}
}
constcacheable = isCacheable(req)
if(cacheable) {
consthit = microCache.get(req.url)
if(hit) {
if(!isProd) {
console.log(`cache hit!`)
}
returnres.end(hit)
}
}
constcontext = {
title:'Vue DB',// default title
url: req.url
}
renderer.renderToString(context,(err,html) => {
if(err) {
returnhandleError(err)
}
res.end(html)
if(cacheable) {
microCache.set(req.url,html)
}
if(!isProd) {
console.log(`whole request:${Date.now() - s}ms`)
}
})
}
app.get('*',isProd ? render : (req,res) => {
readyPromise.then(() => render(req,res))
})
constport = process.env.PORT ||8888
app.listen(port,() => {
console.log(`server started at localhost:${port}`)
})
5、客戶端api文件create-api-client.js
/**
 * Created by lin on 2017/8/25.
 */

import axios from 'axios';
let api;

axios.defaults.baseURL = process.env.API_URL;
axios.defaults.timeout = 10000;

axios.interceptors.response.use((res) => {
  if (res.status >= 200 && res.status < 300) {
    return res;
  }
  return Promise.reject(res);
}, (error) => {
  return Promise.reject({message: '網(wǎng)絡(luò)異常，請刷新重試', err: error});
});

if (process.__API__) {
  api = process.__API__;
} else {
  api = {
    get: function(url) {
      return new Promise((resolve, reject) => {
        axios.get(url).then(res => {
          resolve(res);
        }).catch((error) => {
          reject(error);
        });
      });
    },
    post: function(target, options = {}) {
      return new Promise((resolve, reject) => {
        axios.post(target, options).then(res => {
          resolve(res);
        }).catch((error) => {
          reject(error);
        });
      });
    }
  };
}

export default api;
6、服務(wù)端api文件create-api-server.js
/**
 * Created by lin on 2017/8/25.
 */

import axios from 'axios';
let cook = process.__COOKIE__ || '';
let api;

axios.defaults.baseURL = 'https://api.douban.com/v2/';
axios.defaults.timeout = 10000;

axios.interceptors.response.use((res) => {
  if (res.status >= 200 && res.status < 300) {
    return Promise.resolve(res);
  }
  return Promise.reject(res);
}, (error) => {
  // 網(wǎng)絡(luò)異常
  return Promise.reject({message: '網(wǎng)絡(luò)異常，請刷新重試', err: error, type: 1});
});

if (process.__API__) {
  api = process.__API__;
} else {
  api = {
    get: function(target) {
      return new Promise((resolve, reject) => {
        axios.request({
          url: encodeURI(target),
          method: 'get',
          headers: {
            'Cookie': cook
          }
        }).then(res => {
          resolve(res);
        }).catch((error) => {
          reject(error);
        });
      });
    },
    post: function(target, options = {}) {
      return new Promise((resolve, reject) => {
        axios.request({
          url: target,
          method: 'post',
          headers: {
            'Cookie': cook
          },
          params: options
        }).then(res => {
          resolve(res);
        }).catch((error) => {
          reject(error);
        });
      });
    }
  };
}

export default api;

三、注意事項

問題：window is not defined

答：給用到瀏覽器對象的地方加if (typeof window !== 'undefined') {}，有一些插件里也用到了瀏覽器對象，在使用的地方也加一個條件判斷：

if (typeofwindow !== 'undefined') {
Vue.use(VueAnalytics, {
id: process.env.UA_TRACKING_ID,
router
})
}
問題：用到非Vue系列的插件，如hello.all.js(三方登錄的插件)，需要用的地方才引用，報的錯和問題1一樣。

答：這個時候不能再用import導(dǎo)入，需要使用require，

let hello
if (typeof window !== 'undefined') {
hello = require('hello')
}
問題：引用bootstrap

答：將bootstrap.css和bootstrap.js加入webpack.base.config.js的entry中的vendor中

問題：bootstap需要jquery，此時把jQuery加在vendor中沒用。

答：給webpack.base.config.js的plugins添加一個插件，如：

newwebpack.ProvidePlugin({
$ : "jquery",
jQuery : "jquery",
"window.jQuery" :"jquery"
})

四、例子

git地址：https://github.com/LRithe/ssr-vue
這是一個服務(wù)端渲的例子

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